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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2011 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: DelayedAction.html 689 2013-06-28 19:22:16Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.dellroad.stuff.spring;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.util.Date;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import java.util.concurrent.ScheduledExecutorService;<a name="line.11"></a>
<span class="sourceLineNo">012</span>import java.util.concurrent.ScheduledFuture;<a name="line.12"></a>
<span class="sourceLineNo">013</span>import java.util.concurrent.TimeUnit;<a name="line.13"></a>
<span class="sourceLineNo">014</span>import java.util.concurrent.locks.Lock;<a name="line.14"></a>
<span class="sourceLineNo">015</span><a name="line.15"></a>
<span class="sourceLineNo">016</span>import org.springframework.scheduling.TaskScheduler;<a name="line.16"></a>
<span class="sourceLineNo">017</span><a name="line.17"></a>
<span class="sourceLineNo">018</span>/**<a name="line.18"></a>
<span class="sourceLineNo">019</span> * Manages a delayed action without race conditions.<a name="line.19"></a>
<span class="sourceLineNo">020</span> *<a name="line.20"></a>
<span class="sourceLineNo">021</span> * &lt;p&gt;<a name="line.21"></a>
<span class="sourceLineNo">022</span> * A "delayed action" is a some action that needs to get done by some time in the future.<a name="line.22"></a>
<span class="sourceLineNo">023</span> * &lt;/p&gt;<a name="line.23"></a>
<span class="sourceLineNo">024</span> *<a name="line.24"></a>
<span class="sourceLineNo">025</span> * &lt;p&gt;<a name="line.25"></a>
<span class="sourceLineNo">026</span> * This class does two things:<a name="line.26"></a>
<span class="sourceLineNo">027</span> * &lt;ul&gt;<a name="line.27"></a>
<span class="sourceLineNo">028</span> *  &lt;li&gt;It collapses multiple attempts to schedule the action into a single scheduled action,<a name="line.28"></a>
<span class="sourceLineNo">029</span> *  i.e., at most one outstanding scheduled action can exist at a time.&lt;/li&gt;<a name="line.29"></a>
<span class="sourceLineNo">030</span> *  &lt;li&gt;It provides a race-free and 100% reliable way to {@link #cancel} a future scheduled action, if any.&lt;/li&gt;<a name="line.30"></a>
<span class="sourceLineNo">031</span> * &lt;/ul&gt;<a name="line.31"></a>
<span class="sourceLineNo">032</span> * &lt;/p&gt;<a name="line.32"></a>
<span class="sourceLineNo">033</span> *<a name="line.33"></a>
<span class="sourceLineNo">034</span> * &lt;p&gt;<a name="line.34"></a>
<span class="sourceLineNo">035</span> * The action itself is defined by the subclass' implementation of {@link #run run()}.<a name="line.35"></a>
<span class="sourceLineNo">036</span> * &lt;/p&gt;<a name="line.36"></a>
<span class="sourceLineNo">037</span> *<a name="line.37"></a>
<span class="sourceLineNo">038</span> * &lt;p&gt;<a name="line.38"></a>
<span class="sourceLineNo">039</span> * To avoid races, this class requires the user to supply a &lt;i&gt;locking object&lt;/i&gt;. This may either be a normal<a name="line.39"></a>
<span class="sourceLineNo">040</span> * Java object, in which case normal Java synchronization is used, or a {@link Lock} object. The locking object is<a name="line.40"></a>
<span class="sourceLineNo">041</span> * used to serialize scheduling activity and action invocation. In other words, the locking object is locked during<a name="line.41"></a>
<span class="sourceLineNo">042</span> * the execution of {@link #schedule schedule()}, {@link #cancel cancel()}, and {@link #run run()}.<a name="line.42"></a>
<span class="sourceLineNo">043</span> * &lt;/p&gt;<a name="line.43"></a>
<span class="sourceLineNo">044</span> *<a name="line.44"></a>
<span class="sourceLineNo">045</span> * &lt;p&gt;<a name="line.45"></a>
<span class="sourceLineNo">046</span> * Therefore, any time the locking object is locked, the state of this {@link DelayedAction} instance is "frozen"<a name="line.46"></a>
<span class="sourceLineNo">047</span> * in one of three states: not scheduled, scheduled, or executing (in the latter case, of course the thread doing the<a name="line.47"></a>
<span class="sourceLineNo">048</span> * executing is the one holding the lock). Therefore, to completely avoid race conditions, user code must &lt;i&gt;itself&lt;/i&gt;<a name="line.48"></a>
<span class="sourceLineNo">049</span> * lock the locking object itself prior to invoking any methods in this class.<a name="line.49"></a>
<span class="sourceLineNo">050</span> * &lt;/p&gt;<a name="line.50"></a>
<span class="sourceLineNo">051</span> *<a name="line.51"></a>
<span class="sourceLineNo">052</span> * &lt;p&gt;<a name="line.52"></a>
<span class="sourceLineNo">053</span> * Typically the most convenient locking object to use is the user's own {@code this} object, which can be locked using a<a name="line.53"></a>
<span class="sourceLineNo">054</span> * {@code synchronized} method or block.<a name="line.54"></a>
<span class="sourceLineNo">055</span> * &lt;/p&gt;<a name="line.55"></a>
<span class="sourceLineNo">056</span> *<a name="line.56"></a>
<span class="sourceLineNo">057</span> * &lt;p&gt;<a name="line.57"></a>
<span class="sourceLineNo">058</span> * Note: in the case that {@link #run run()} invokes {@link Object#wait Object.wait()} on the locking object, thereby<a name="line.58"></a>
<span class="sourceLineNo">059</span> * temporarily releasing the lock, to any other methods in this class it will appear as if that execution has already<a name="line.59"></a>
<span class="sourceLineNo">060</span> * completed.<a name="line.60"></a>
<span class="sourceLineNo">061</span> */<a name="line.61"></a>
<span class="sourceLineNo">062</span>public abstract class DelayedAction implements Runnable {<a name="line.62"></a>
<span class="sourceLineNo">063</span><a name="line.63"></a>
<span class="sourceLineNo">064</span>    private final Lock lock;<a name="line.64"></a>
<span class="sourceLineNo">065</span>    private final Object objLock;<a name="line.65"></a>
<span class="sourceLineNo">066</span>    private final TaskScheduler taskScheduler;<a name="line.66"></a>
<span class="sourceLineNo">067</span>    private final ScheduledExecutorService executorService;<a name="line.67"></a>
<span class="sourceLineNo">068</span><a name="line.68"></a>
<span class="sourceLineNo">069</span>    private ScheduledFuture&lt;?&gt; future;<a name="line.69"></a>
<span class="sourceLineNo">070</span>    private Date futureDate;<a name="line.70"></a>
<span class="sourceLineNo">071</span><a name="line.71"></a>
<span class="sourceLineNo">072</span>    /**<a name="line.72"></a>
<span class="sourceLineNo">073</span>     * Constructor utitilizing a {@link TaskScheduler} and normal Java object locking.<a name="line.73"></a>
<span class="sourceLineNo">074</span>     *<a name="line.74"></a>
<span class="sourceLineNo">075</span>     * @param lock locking object used to serialize activity, or null for {@code this}<a name="line.75"></a>
<span class="sourceLineNo">076</span>     * @param taskScheduler scheduler object<a name="line.76"></a>
<span class="sourceLineNo">077</span>     * @throws IllegalArgumentException if {@code taskScheduler} is null<a name="line.77"></a>
<span class="sourceLineNo">078</span>     */<a name="line.78"></a>
<span class="sourceLineNo">079</span>    protected DelayedAction(Object lock, TaskScheduler taskScheduler) {<a name="line.79"></a>
<span class="sourceLineNo">080</span>        this(null, lock, taskScheduler, null);<a name="line.80"></a>
<span class="sourceLineNo">081</span>        if (taskScheduler == null)<a name="line.81"></a>
<span class="sourceLineNo">082</span>            throw new IllegalArgumentException("null taskScheduler");<a name="line.82"></a>
<span class="sourceLineNo">083</span>    }<a name="line.83"></a>
<span class="sourceLineNo">084</span><a name="line.84"></a>
<span class="sourceLineNo">085</span>    /**<a name="line.85"></a>
<span class="sourceLineNo">086</span>     * Constructor utitilizing a {@link ScheduledExecutorService} and normal Java object locking.<a name="line.86"></a>
<span class="sourceLineNo">087</span>     *<a name="line.87"></a>
<span class="sourceLineNo">088</span>     * @param lock locking object used to serialize activity, or null for {@code this}<a name="line.88"></a>
<span class="sourceLineNo">089</span>     * @param executorService scheduler object<a name="line.89"></a>
<span class="sourceLineNo">090</span>     * @throws IllegalArgumentException if {@code executorService} is null<a name="line.90"></a>
<span class="sourceLineNo">091</span>     */<a name="line.91"></a>
<span class="sourceLineNo">092</span>    protected DelayedAction(Object lock, ScheduledExecutorService executorService) {<a name="line.92"></a>
<span class="sourceLineNo">093</span>        this(null, lock, null, executorService);<a name="line.93"></a>
<span class="sourceLineNo">094</span>        if (executorService == null)<a name="line.94"></a>
<span class="sourceLineNo">095</span>            throw new IllegalArgumentException("null executorService");<a name="line.95"></a>
<span class="sourceLineNo">096</span>    }<a name="line.96"></a>
<span class="sourceLineNo">097</span><a name="line.97"></a>
<span class="sourceLineNo">098</span>    /**<a name="line.98"></a>
<span class="sourceLineNo">099</span>     * Constructor utitilizing a {@link TaskScheduler} and a {@link Lock} for locking.<a name="line.99"></a>
<span class="sourceLineNo">100</span>     *<a name="line.100"></a>
<span class="sourceLineNo">101</span>     * @param lock locking object used to serialize activity<a name="line.101"></a>
<span class="sourceLineNo">102</span>     * @param taskScheduler scheduler object<a name="line.102"></a>
<span class="sourceLineNo">103</span>     * @throws IllegalArgumentException if {@code lock} is null<a name="line.103"></a>
<span class="sourceLineNo">104</span>     * @throws IllegalArgumentException if {@code taskScheduler} is null<a name="line.104"></a>
<span class="sourceLineNo">105</span>     */<a name="line.105"></a>
<span class="sourceLineNo">106</span>    protected DelayedAction(Lock lock, TaskScheduler taskScheduler) {<a name="line.106"></a>
<span class="sourceLineNo">107</span>        this(lock, null, taskScheduler, null);<a name="line.107"></a>
<span class="sourceLineNo">108</span>        if (lock == null)<a name="line.108"></a>
<span class="sourceLineNo">109</span>            throw new IllegalArgumentException("null lock");<a name="line.109"></a>
<span class="sourceLineNo">110</span>        if (taskScheduler == null)<a name="line.110"></a>
<span class="sourceLineNo">111</span>            throw new IllegalArgumentException("null taskScheduler");<a name="line.111"></a>
<span class="sourceLineNo">112</span>    }<a name="line.112"></a>
<span class="sourceLineNo">113</span><a name="line.113"></a>
<span class="sourceLineNo">114</span>    /**<a name="line.114"></a>
<span class="sourceLineNo">115</span>     * Constructor utitilizing a {@link ScheduledExecutorService} and a {@link Lock} for locking.<a name="line.115"></a>
<span class="sourceLineNo">116</span>     *<a name="line.116"></a>
<span class="sourceLineNo">117</span>     * @param lock locking object used to serialize activity<a name="line.117"></a>
<span class="sourceLineNo">118</span>     * @param executorService scheduler object<a name="line.118"></a>
<span class="sourceLineNo">119</span>     * @throws IllegalArgumentException if {@code lock} is null<a name="line.119"></a>
<span class="sourceLineNo">120</span>     * @throws IllegalArgumentException if {@code executorService} is null<a name="line.120"></a>
<span class="sourceLineNo">121</span>     */<a name="line.121"></a>
<span class="sourceLineNo">122</span>    protected DelayedAction(Lock lock, ScheduledExecutorService executorService) {<a name="line.122"></a>
<span class="sourceLineNo">123</span>        this(lock, null, null, executorService);<a name="line.123"></a>
<span class="sourceLineNo">124</span>        if (lock == null)<a name="line.124"></a>
<span class="sourceLineNo">125</span>            throw new IllegalArgumentException("null lock");<a name="line.125"></a>
<span class="sourceLineNo">126</span>        if (executorService == null)<a name="line.126"></a>
<span class="sourceLineNo">127</span>            throw new IllegalArgumentException("null executorService");<a name="line.127"></a>
<span class="sourceLineNo">128</span>    }<a name="line.128"></a>
<span class="sourceLineNo">129</span><a name="line.129"></a>
<span class="sourceLineNo">130</span>    private DelayedAction(Lock lock, Object objLock, TaskScheduler taskScheduler, ScheduledExecutorService executorService) {<a name="line.130"></a>
<span class="sourceLineNo">131</span>        this.lock = lock;<a name="line.131"></a>
<span class="sourceLineNo">132</span>        this.objLock = lock != null ? null : objLock != null ? objLock : this;<a name="line.132"></a>
<span class="sourceLineNo">133</span>        this.taskScheduler = taskScheduler;<a name="line.133"></a>
<span class="sourceLineNo">134</span>        this.executorService = executorService;<a name="line.134"></a>
<span class="sourceLineNo">135</span>    }<a name="line.135"></a>
<span class="sourceLineNo">136</span><a name="line.136"></a>
<span class="sourceLineNo">137</span>    /**<a name="line.137"></a>
<span class="sourceLineNo">138</span>     * Schedule the delayed action for the given time.<a name="line.138"></a>
<span class="sourceLineNo">139</span>     *<a name="line.139"></a>
<span class="sourceLineNo">140</span>     * &lt;p&gt;<a name="line.140"></a>
<span class="sourceLineNo">141</span>     * More precisely:<a name="line.141"></a>
<span class="sourceLineNo">142</span>     * &lt;ul&gt;<a name="line.142"></a>
<span class="sourceLineNo">143</span>     *  &lt;li&gt;If an action currently executing, before doing anything else this method blocks until it completes;<a name="line.143"></a>
<span class="sourceLineNo">144</span>     *  if this behavior is undesirable, the caller can avoid this behavior by synchronizing on the locking object<a name="line.144"></a>
<span class="sourceLineNo">145</span>     *  prior to invoking this method.&lt;/li&gt;<a name="line.145"></a>
<span class="sourceLineNo">146</span>     *  &lt;li&gt;If no action is scheduled, one is scheduled for the given time.&lt;/li&gt;<a name="line.146"></a>
<span class="sourceLineNo">147</span>     *  &lt;li&gt;If an action is already scheduled, and the given time is on or after the scheduled time, nothing changes.&lt;/li&gt;<a name="line.147"></a>
<span class="sourceLineNo">148</span>     *  &lt;li&gt;If an action is already scheduled, and the given time is prior to the scheduled time,<a name="line.148"></a>
<span class="sourceLineNo">149</span>     *  the action is rescheduled for the earlier time.&lt;/li&gt;<a name="line.149"></a>
<span class="sourceLineNo">150</span>     * &lt;/ul&gt;<a name="line.150"></a>
<span class="sourceLineNo">151</span>     * &lt;/p&gt;<a name="line.151"></a>
<span class="sourceLineNo">152</span>     *<a name="line.152"></a>
<span class="sourceLineNo">153</span>     * &lt;p&gt;<a name="line.153"></a>
<span class="sourceLineNo">154</span>     * The net result is that, for any invocation, this method guarantees exactly one execution of the action will<a name="line.154"></a>
<span class="sourceLineNo">155</span>     * occur approximately on or before the given date; however, multiple invocations of this method prior to action<a name="line.155"></a>
<span class="sourceLineNo">156</span>     * execution can only ever result in a single "shared" action.<a name="line.156"></a>
<span class="sourceLineNo">157</span>     * &lt;/p&gt;<a name="line.157"></a>
<span class="sourceLineNo">158</span>     *<a name="line.158"></a>
<span class="sourceLineNo">159</span>     * @param date scheduled execution time (at the latest)<a name="line.159"></a>
<span class="sourceLineNo">160</span>     * @throws IllegalArgumentException if {@code date} is null<a name="line.160"></a>
<span class="sourceLineNo">161</span>     * @throws org.springframework.core.task.TaskRejectedException<a name="line.161"></a>
<span class="sourceLineNo">162</span>     *  if the given task was not accepted for internal reasons (e.g. a pool overload handling policy<a name="line.162"></a>
<span class="sourceLineNo">163</span>     *  or a pool shutdown in progress)<a name="line.163"></a>
<span class="sourceLineNo">164</span>     */<a name="line.164"></a>
<span class="sourceLineNo">165</span>    public void schedule(final Date date) {<a name="line.165"></a>
<span class="sourceLineNo">166</span>        this.runLocked(new Runnable() {<a name="line.166"></a>
<span class="sourceLineNo">167</span>            @Override<a name="line.167"></a>
<span class="sourceLineNo">168</span>            public void run() {<a name="line.168"></a>
<span class="sourceLineNo">169</span>                DelayedAction.this.scheduleWhileLocked(date);<a name="line.169"></a>
<span class="sourceLineNo">170</span>            }<a name="line.170"></a>
<span class="sourceLineNo">171</span>        });<a name="line.171"></a>
<span class="sourceLineNo">172</span>    }<a name="line.172"></a>
<span class="sourceLineNo">173</span>    private void scheduleWhileLocked(final Date date) {<a name="line.173"></a>
<span class="sourceLineNo">174</span><a name="line.174"></a>
<span class="sourceLineNo">175</span>        // Sanity check<a name="line.175"></a>
<span class="sourceLineNo">176</span>        if (date == null)<a name="line.176"></a>
<span class="sourceLineNo">177</span>            throw new IllegalArgumentException("null date");<a name="line.177"></a>
<span class="sourceLineNo">178</span><a name="line.178"></a>
<span class="sourceLineNo">179</span>        // Already scheduled?<a name="line.179"></a>
<span class="sourceLineNo">180</span>        if (this.future != null) {<a name="line.180"></a>
<span class="sourceLineNo">181</span><a name="line.181"></a>
<span class="sourceLineNo">182</span>            // Requested time is after scheduled time? Note: must be "&gt;=", not "&gt;" to ensure monotonically increasing Dates<a name="line.182"></a>
<span class="sourceLineNo">183</span>            if (date.compareTo(this.futureDate) &gt;= 0)<a name="line.183"></a>
<span class="sourceLineNo">184</span>                return;<a name="line.184"></a>
<span class="sourceLineNo">185</span><a name="line.185"></a>
<span class="sourceLineNo">186</span>            // Cancel it<a name="line.186"></a>
<span class="sourceLineNo">187</span>            this.cancel();<a name="line.187"></a>
<span class="sourceLineNo">188</span>        }<a name="line.188"></a>
<span class="sourceLineNo">189</span><a name="line.189"></a>
<span class="sourceLineNo">190</span>        // Schedule it<a name="line.190"></a>
<span class="sourceLineNo">191</span>        this.future = this.schedule(new Runnable() {<a name="line.191"></a>
<span class="sourceLineNo">192</span>            @Override<a name="line.192"></a>
<span class="sourceLineNo">193</span>            public void run() {<a name="line.193"></a>
<span class="sourceLineNo">194</span>                DelayedAction.this.futureInvoked(date);<a name="line.194"></a>
<span class="sourceLineNo">195</span>            }<a name="line.195"></a>
<span class="sourceLineNo">196</span>        }, date);<a name="line.196"></a>
<span class="sourceLineNo">197</span>        this.futureDate = date;<a name="line.197"></a>
<span class="sourceLineNo">198</span>    }<a name="line.198"></a>
<span class="sourceLineNo">199</span><a name="line.199"></a>
<span class="sourceLineNo">200</span>    /**<a name="line.200"></a>
<span class="sourceLineNo">201</span>     * Cancel the future scheduled action, if any.<a name="line.201"></a>
<span class="sourceLineNo">202</span>     *<a name="line.202"></a>
<span class="sourceLineNo">203</span>     * &lt;p&gt;<a name="line.203"></a>
<span class="sourceLineNo">204</span>     * More precisely:<a name="line.204"></a>
<span class="sourceLineNo">205</span>     * &lt;ul&gt;<a name="line.205"></a>
<span class="sourceLineNo">206</span>     *  &lt;li&gt;If an action currently executing, before doing anything else this method blocks until it completes;<a name="line.206"></a>
<span class="sourceLineNo">207</span>     *  if this behavior is undesirable, the caller can avoid this behavior by synchronizing on the locking object<a name="line.207"></a>
<span class="sourceLineNo">208</span>     *  prior to invoking this method.&lt;/li&gt;<a name="line.208"></a>
<span class="sourceLineNo">209</span>     *  &lt;li&gt;If an action is scheduled but has not started yet, it is guaranteed not to run.&lt;/li&gt;<a name="line.209"></a>
<span class="sourceLineNo">210</span>     *  &lt;li&gt;If no action is scheduled or executing, nothing changes.&lt;/li&gt;<a name="line.210"></a>
<span class="sourceLineNo">211</span>     * &lt;/ul&gt;<a name="line.211"></a>
<span class="sourceLineNo">212</span>     * &lt;/p&gt;<a name="line.212"></a>
<span class="sourceLineNo">213</span>     */<a name="line.213"></a>
<span class="sourceLineNo">214</span>    public void cancel() {<a name="line.214"></a>
<span class="sourceLineNo">215</span>        this.runLocked(new Runnable() {<a name="line.215"></a>
<span class="sourceLineNo">216</span>            @Override<a name="line.216"></a>
<span class="sourceLineNo">217</span>            public void run() {<a name="line.217"></a>
<span class="sourceLineNo">218</span>                DelayedAction.this.cancelWhileLocked();<a name="line.218"></a>
<span class="sourceLineNo">219</span>            }<a name="line.219"></a>
<span class="sourceLineNo">220</span>        });<a name="line.220"></a>
<span class="sourceLineNo">221</span>    }<a name="line.221"></a>
<span class="sourceLineNo">222</span>    private void cancelWhileLocked() {<a name="line.222"></a>
<span class="sourceLineNo">223</span><a name="line.223"></a>
<span class="sourceLineNo">224</span>        // Anything to do?<a name="line.224"></a>
<span class="sourceLineNo">225</span>        if (this.future == null)<a name="line.225"></a>
<span class="sourceLineNo">226</span>            return;<a name="line.226"></a>
<span class="sourceLineNo">227</span><a name="line.227"></a>
<span class="sourceLineNo">228</span>        // Cancel future<a name="line.228"></a>
<span class="sourceLineNo">229</span>        this.future.cancel(false);<a name="line.229"></a>
<span class="sourceLineNo">230</span>        this.future = null;<a name="line.230"></a>
<span class="sourceLineNo">231</span>        this.futureDate = null;<a name="line.231"></a>
<span class="sourceLineNo">232</span>    }<a name="line.232"></a>
<span class="sourceLineNo">233</span><a name="line.233"></a>
<span class="sourceLineNo">234</span>    /**<a name="line.234"></a>
<span class="sourceLineNo">235</span>     * Determine whether there is currently an outstanding scheduled action.<a name="line.235"></a>
<span class="sourceLineNo">236</span>     */<a name="line.236"></a>
<span class="sourceLineNo">237</span>    public boolean isScheduled() {<a name="line.237"></a>
<span class="sourceLineNo">238</span>        final boolean[] result = new boolean[1];<a name="line.238"></a>
<span class="sourceLineNo">239</span>        this.runLocked(new Runnable() {<a name="line.239"></a>
<span class="sourceLineNo">240</span>            @Override<a name="line.240"></a>
<span class="sourceLineNo">241</span>            public void run() {<a name="line.241"></a>
<span class="sourceLineNo">242</span>                result[0] = DelayedAction.this.future != null;<a name="line.242"></a>
<span class="sourceLineNo">243</span>            }<a name="line.243"></a>
<span class="sourceLineNo">244</span>        });<a name="line.244"></a>
<span class="sourceLineNo">245</span>        return result[0];<a name="line.245"></a>
<span class="sourceLineNo">246</span>    }<a name="line.246"></a>
<span class="sourceLineNo">247</span><a name="line.247"></a>
<span class="sourceLineNo">248</span>    /**<a name="line.248"></a>
<span class="sourceLineNo">249</span>     * Get the scheduled time for the outstanding scheduled action, if any.<a name="line.249"></a>
<span class="sourceLineNo">250</span>     *<a name="line.250"></a>
<span class="sourceLineNo">251</span>     * @return oustanding action scheduled time, or null if there is no scheduled action<a name="line.251"></a>
<span class="sourceLineNo">252</span>     */<a name="line.252"></a>
<span class="sourceLineNo">253</span>    public Date getScheduledTime() {<a name="line.253"></a>
<span class="sourceLineNo">254</span>        final Date[] result = new Date[1];<a name="line.254"></a>
<span class="sourceLineNo">255</span>        this.runLocked(new Runnable() {<a name="line.255"></a>
<span class="sourceLineNo">256</span>            @Override<a name="line.256"></a>
<span class="sourceLineNo">257</span>            public void run() {<a name="line.257"></a>
<span class="sourceLineNo">258</span>                result[0] = DelayedAction.this.futureDate;<a name="line.258"></a>
<span class="sourceLineNo">259</span>            }<a name="line.259"></a>
<span class="sourceLineNo">260</span>        });<a name="line.260"></a>
<span class="sourceLineNo">261</span>        return result[0];<a name="line.261"></a>
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<span class="sourceLineNo">263</span><a name="line.263"></a>
<span class="sourceLineNo">264</span>    /**<a name="line.264"></a>
<span class="sourceLineNo">265</span>     * Schedule the given action using the task scheduler passed to the constructor.<a name="line.265"></a>
<span class="sourceLineNo">266</span>     * Use of this method does not change the state of this instance.<a name="line.266"></a>
<span class="sourceLineNo">267</span>     *<a name="line.267"></a>
<span class="sourceLineNo">268</span>     * @param action action to perform<a name="line.268"></a>
<span class="sourceLineNo">269</span>     * @param date when to perform it<a name="line.269"></a>
<span class="sourceLineNo">270</span>     * @throws IllegalArgumentException if either parameter is null<a name="line.270"></a>
<span class="sourceLineNo">271</span>     * @throws java.util.concurrent.RejectedExecutionException<a name="line.271"></a>
<span class="sourceLineNo">272</span>     *   if the given task was not accepted for internal reasons (e.g. a pool overload handling<a name="line.272"></a>
<span class="sourceLineNo">273</span>     *  policy or a pool shutdown in progress)<a name="line.273"></a>
<span class="sourceLineNo">274</span>     */<a name="line.274"></a>
<span class="sourceLineNo">275</span>    protected ScheduledFuture&lt;?&gt; schedule(Runnable action, Date date) {<a name="line.275"></a>
<span class="sourceLineNo">276</span>        if (action == null)<a name="line.276"></a>
<span class="sourceLineNo">277</span>            throw new IllegalArgumentException("null action");<a name="line.277"></a>
<span class="sourceLineNo">278</span>        if (date == null)<a name="line.278"></a>
<span class="sourceLineNo">279</span>            throw new IllegalArgumentException("null date");<a name="line.279"></a>
<span class="sourceLineNo">280</span>        if (this.taskScheduler != null)<a name="line.280"></a>
<span class="sourceLineNo">281</span>            return this.taskScheduler.schedule(action, date);<a name="line.281"></a>
<span class="sourceLineNo">282</span>        long now = System.currentTimeMillis();<a name="line.282"></a>
<span class="sourceLineNo">283</span>        long when = date.getTime();<a name="line.283"></a>
<span class="sourceLineNo">284</span>        if (when &lt; now)<a name="line.284"></a>
<span class="sourceLineNo">285</span>            when = now;<a name="line.285"></a>
<span class="sourceLineNo">286</span>        return this.executorService.schedule(action, when - now, TimeUnit.MILLISECONDS);<a name="line.286"></a>
<span class="sourceLineNo">287</span>    }<a name="line.287"></a>
<span class="sourceLineNo">288</span><a name="line.288"></a>
<span class="sourceLineNo">289</span>    // Do the action<a name="line.289"></a>
<span class="sourceLineNo">290</span>    private void futureInvoked(final Date date) {<a name="line.290"></a>
<span class="sourceLineNo">291</span>        this.runLocked(new Runnable() {<a name="line.291"></a>
<span class="sourceLineNo">292</span>            @Override<a name="line.292"></a>
<span class="sourceLineNo">293</span>            public void run() {<a name="line.293"></a>
<span class="sourceLineNo">294</span>                DelayedAction.this.futureInvokedWhileLocked(date);<a name="line.294"></a>
<span class="sourceLineNo">295</span>            }<a name="line.295"></a>
<span class="sourceLineNo">296</span>        });<a name="line.296"></a>
<span class="sourceLineNo">297</span>    }<a name="line.297"></a>
<span class="sourceLineNo">298</span>    private void futureInvokedWhileLocked(Date date) {<a name="line.298"></a>
<span class="sourceLineNo">299</span><a name="line.299"></a>
<span class="sourceLineNo">300</span>        // Handle race condition where future.cancel() fails<a name="line.300"></a>
<span class="sourceLineNo">301</span>        if (this.futureDate != date)<a name="line.301"></a>
<span class="sourceLineNo">302</span>            return;<a name="line.302"></a>
<span class="sourceLineNo">303</span><a name="line.303"></a>
<span class="sourceLineNo">304</span>        // Reset state<a name="line.304"></a>
<span class="sourceLineNo">305</span>        this.future = null;<a name="line.305"></a>
<span class="sourceLineNo">306</span>        this.futureDate = null;<a name="line.306"></a>
<span class="sourceLineNo">307</span><a name="line.307"></a>
<span class="sourceLineNo">308</span>        // Perform action<a name="line.308"></a>
<span class="sourceLineNo">309</span>        this.run();<a name="line.309"></a>
<span class="sourceLineNo">310</span>    }<a name="line.310"></a>
<span class="sourceLineNo">311</span><a name="line.311"></a>
<span class="sourceLineNo">312</span>    // Invoke action while locked<a name="line.312"></a>
<span class="sourceLineNo">313</span>    private void runLocked(Runnable action) {<a name="line.313"></a>
<span class="sourceLineNo">314</span>        if (this.objLock != null) {<a name="line.314"></a>
<span class="sourceLineNo">315</span>            synchronized (this.objLock) {<a name="line.315"></a>
<span class="sourceLineNo">316</span>                action.run();<a name="line.316"></a>
<span class="sourceLineNo">317</span>            }<a name="line.317"></a>
<span class="sourceLineNo">318</span>        } else {<a name="line.318"></a>
<span class="sourceLineNo">319</span>            this.lock.lock();<a name="line.319"></a>
<span class="sourceLineNo">320</span>            try {<a name="line.320"></a>
<span class="sourceLineNo">321</span>                action.run();<a name="line.321"></a>
<span class="sourceLineNo">322</span>            } finally {<a name="line.322"></a>
<span class="sourceLineNo">323</span>                this.lock.unlock();<a name="line.323"></a>
<span class="sourceLineNo">324</span>            }<a name="line.324"></a>
<span class="sourceLineNo">325</span>        }<a name="line.325"></a>
<span class="sourceLineNo">326</span>    }<a name="line.326"></a>
<span class="sourceLineNo">327</span>}<a name="line.327"></a>
<span class="sourceLineNo">328</span><a name="line.328"></a>




























































</pre>
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